#!usr/bin/node

const {Readable} = require("stream");

class MyReadable extends Readable{
  constructor() {
    super();
  }
  _read() {
    if(c > 'z'.charCodeAt(0)) {
      this.push(null);
      return ;
    }
    this.push(String.fromCharCode(c++));
  }
}

const rd = new MyReadable();

let c = 'a'.charCodeAt(0);

rd.pipe(process.stdout);
